Messages in this thread | | | Date | Tue, 10 Nov 2009 12:01:47 -0800 | From | "H. Peter Anvin" <> | Subject | Re: i686 quirk for AMD Geode |
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On 11/10/2009 11:50 AM, Avi Kivity wrote: >> >> Consider SSE3, for example. Why should the same concept not apply to >> SSE3 instructions as to CMOV? > > Because then user programs would run 20x or more slower than the user > expects. Better to terminate early (and teach userspace how to choose > the instruction subset correctly). >
I picked the example carefully: SSE3 is a small set of instructions which probably aren't used very heavily. In that sense, it has *exactly* the same properties as CMOV - if you have the source, you're better off recompiling, but it *might* help you if you happen to only have a binary.
What I want people to understand is that this is a *huge* rathole, and it doesn't have any obvious bottom that I can see.
-hpa
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